Chaotic inflation with kinetic alignment of axion fields

N-flation is a radiatively stable scenario for chaotic inflation in which the displacements of N≫1 axions with decay constants f1≤…≤fN<MP lead to a super-Planckian effective displacement equal to the Pythagorean sum fPy of the fi. We show that mixing in the axion kinetic term generically leads to the phenomenon of kinetic alignment, allowing for effective displacements as large as N−−√fN≥fPy, even if f1,…,fN−1 are arbitrarily small. At the level of kinematics, the necessary alignment occurs with very high probability, because of eigenvector delocalization. We present conditions under which inflation can take place along an aligned direction. Our construction sharply reduces the challenge of realizing N-flation in string theory

Sex differences in scholastic attainment from year 3 to form IV : a study of trends

The role of pupil sex as one of the major determinants of scholastic performance is amply demonstrated in the international literature. Studies of primary school children carried out in the UK and the USA generally indicate that whatever sex differences exist in scholastic performance these tend to emerge clearly and consistently after age 11 (cf. Badger, 1985; Fairweather, 1976; Shackleton & Fletcher, 1984; Shuard, 1982). Studies by Ross & Simpson (1971), Thompson (1975) and Wilson (1972), for instance, show that in verbal abilities like reading and spelling no clear cut boy-girl differences appear before this age. Studies by Kellmer Pringle, Butler & Davie (1966) and Pidgeon (1960) similarly suggest that this is also the case for arithmetic skills and mathematical ability. In a comprehensive review of the literature on sex differences, Maccoby & Jacklin ( 197 4) conclude that up to age 11 boys and girls are very similar in verbal and mathematical abilities. At age 11, however, their abilities begin to diverge with girls becoming superior in verbal abilities and boys in mathematical abilities. Borg & Falzon (1995) propose a plausible explanation for the little or no consistency in the occurrence and direction of sex differences. They argue that this may lie in the nature of the items making up the assessment instrument. Indeed, in a report on mathematical performance at age 11, the Assessment of Performance Unit (1980) found that when the examination paper is analysed in its component parts rather than as a whole paper girls perform significantly better than boys in certain areas such as computation while boys perform better in other areas like the spatial (e.g. length , area, volume and capacity). Borg & Falzon ( 1995) postulate that this may also well be the case in language subjects so that it is quite possible, for instance, to find girls performing better in one specific language area and boys in another. Hence, differ- ences and directions may well be the product of the weighting of the various abilities assessed by the instrument. Although these UK and USA findings on sex differences may be important and interesting and may have serious implications for educational policies and practices it is here argued that they are not, or should be, directly transferable to the local situation. Cultural differences as well as differences in parental practices, educational philosophies and classroom practices warrant that sex differences in performance in school subjects should be studied in the local context. A small number of Maltese studies have begun to address this need. Falzon & Sammut (1976), for instance, found that amongst Maltese Form I and Il pupils in comprehensive schools girls consistently score higher in Maltese, English, and Maths, with the greatest differences occurring ip the two languages. Moreover, Ventura (1992) reports that whereas in Forms I and II girls outperform boys in Integrated Science, in Forms Ill and IV there are no sex differences in performance in Biology and Chemistry; in Physics, however, the boys perform better.peer-reviewe

Relation-changing modal operators

We study dynamic modal operators that can change the accessibility relation of a model during the evaluation of a formula. In particular, we extend the basic modal language with modalities that are able to delete, add or swap an edge between pairs of elements of the domain. We define a generic framework to characterize this kind of operations. First, we investigate relation-changing modal logics as fragments of classical logics. Then, we use the new framework to get a suitable notion of bisimulation for the logics introduced, and we investigate their expressive power. Finally, we show that the complexity of the model checking problem for the particular operators introduced is PSpace-complete, and we study two subproblems of model checking: formula complexity and program complexity.Fil: Areces, Carlos Eduardo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fervari, Raul Alberto. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hoffmann, Guillaume Emmanuel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Front Cover, Publication Information

Front Cover, Publication Information, Table of Content

Rocket studies of the lower ionosphere

The earth's ionosphere in the altitude range of 50 to 200 km was investigated by rocket-borne sensors, supplemented by ground-based measurement. The rocket payloads included mass spectrometers, energetic particle detectors, Langmuir probes and radio propagation experiments. Where possible, rocket flights were included in studies of specific phenomena, and the availability of data from other experiments greatly increased the significance of the results. The principal ionospheric phenomena studied were: winter anomaly in radiowave absorption, ozone and molecular oxygen densities, mid-latitude sporadic-E layers, energetic particle precipitation at middle and low latitudes, ionospheric instabilities and turbulence, and solar eclipse effects in the D and E regions. This document lists personnel who worked on the project, and provides a bibliography of resultant publications

Designing Decidable Logics of Epistemology

We investigate the following “epistemic” extensions of (fragments of) first order logics: if phi is a formula, then box_i phi (i in I) is also a formula, where I is a fixed finite set. The intended meaning of box_i phi is “the i-th agent (ith participant of the model) knows phi”. The main result of the paper is Theorem 1: if L is such a fragment of first order logic whose consequence relation is weakly decidable, then the consequence relation of the epistemic extension of L remains weakly decidable, as well